Enchanted Glass
Diana Wynne Jones2010

Enchanted Glass is set in the imaginary town of Melstone, England. Near the town of Melstone is Melstone House, an old place which Andrew Hope has inherited from his grandfather. With Melstone House comes a "field-of-care" which is a region of magical responsibility. Unfortunately, Andrew does not quite grasp the full implications of this, causing many of the problems in the story.
Shortly after Andrew takes possession of Melstone House, Aidan Cain appears on his doorstep, asking for help. His recently deceased grandmother had told him that the owner of Melstone House could help him, if he ever needed it. Aidan is being pursued by an unknown force, which turns out to be the fairy king Oberon, who thinks he is his son.
Together, Andrew and Aidan must unravel the mystery of Melstone House, and gain control of their magic.